x/m = kP^$\frac{1}{n}$, where x = mass of gas adsorbed, m = mass of adsorbent, P = pressure, k and n are constants (n > 1). Logarithmic form: log$\frac{x}{m}$ = log k + $\frac{1}{n}$ log P. Plot of log$\frac{x}{m}$ vs log P: straight line with slope = 1/n and intercept = log k. At low pressure: x/m is proportional to P $\frac{1}{n approaches 1}$. At high pressure: x/m approaches constant $\frac{1}{n approaches 0}$. Freundlich isotherm fails at very high pressures (doesn't predict saturation properly). Valid only over limited pressure range.